Remove support for 'disabled' files in plugins

[Klap-in]

The current mechanism is that the disabled plugins are stored in conf/plugins.local.php
At the moment the lib/plugins/[plugin]/disabled files are deprecated since 2011, but still available.

https://github.com/splitbrain/dokuwiki/blob/master/inc/plugincontroller.class.php#L166

[Klap-in]

The condition || ($plugin === 'plugin' && isset($conf['pluginmanager']) && !$conf['pluginmanager']) remains from the previous plugin manager.
I will remove it as well.
more background: c45608d

Question:

               if (substr($plugin,-9) == '.disabled') {
                    // the plugin was disabled by rc2009-01-26
                    // disabling mechanism was changed back very soon again
                    // to keep everything simple we just skip the plugin completely
                    continue;
                } else

Is it ok for you, to remove this <pluginfoldername>.disable feature too?

[splitbrain]

Yes, that should go too.